# Why does the composition of Ocean Water list sodium and chloride separately?

This is the site I am using.

It is also found here, but this uses mg/L instead of percents.

It lists Sodium at 30.8%, and Chloride at 55.3%. How can this be? Shouldn't the two be listed as Sodium Chloride or salt? Because as far as I know, there is no way to obtain chloride on its own.

• It's not like they just float there in the form of $\ce{NaCl}$, either. Jul 6, 2016 at 12:31
• @IvanNeretin What do you mean Jul 6, 2016 at 12:36
• Forget it. Let's put it this way: yes, these two could be listed together as $\ce{NaCl}$, but the authors chose otherwise. This is entirely legitimate and meaningful, even though you can't isolate $\ce{Cl-}$ on its own. Jul 6, 2016 at 12:40
• Giving a NaCl content is nonsense. If you had put together the numbers, you would've found they don't match. 55.3 g / 35.4 (g/mol) = 1.5 chloride, 30.8 / 23 (g/mol) = 1.3 sodium. There are a lot of other ions in the sea, with magnesium and sulfate making up most of the difference. en.wikipedia.org/wiki/Seawater#Origin
– Karl
Jul 6, 2016 at 13:11

First of all, of course you could provide NaCl content as a weight or molar percentage, and I can demonstrate if necessary.

However, this doesn't really reflect the reality: ocean water is a solution of many salts. Chloride does not necessarily only come from NaCl, but can also come from KCl, MgCl$_2$, and so on. All the ions are solved individually, and if you start evaporating the water, you will get a mix of salts.

So there's really no point in showing NaCl percentage.

Of course, you're right in that it is impossible to obtain pure chloride ions. But the chlorides you will obtain will not necessarily be those of sodium.

• Thanks! Is there anyway I can find somewhere where it lists it as NaCl and MgCl2, etc Jul 6, 2016 at 23:51
• @SuperNinja741DoesGaming Do you mean like a brand of water, or are you interested in the calculation? I'm not sure what you are asking about.
– Zubo
Jul 22, 2016 at 8:57
• still for ocean water Jul 22, 2016 at 15:11
• @SuperNinja741DoesGaming sorry for the late answer, I was away... here's the thing - if you want the composition listed in compounds rather than ions (i.e. NaCl - x g/L instead of Na+ - y g/L, Cl- - z g/L), then that might depend on the way the sea water is evaporated, and will very much depend on what sea water we are talking about (concentrations differ a lot). I've found this paper jsedres.sepmonline.org/content/57/5/928.full.pdf+html , but can't access it at the moment. It may contain what you are interested in.
– Zubo
Sep 22, 2016 at 16:21
• @SuperNinja741DoesGaming Also, there's this hydrochemistry.eu/exmpls/sea_evap.html , but I'm not sure if that helps. Sorry for not having a better answer. I can, of course, show how to calculate the THEORETICAL MAXIMUM of NaCl in a certain sea water, but I'm not sure if that would actually precipitate in reality. Let me know if you are still interested.
– Zubo
Sep 22, 2016 at 16:24